The risk of falling ill from a Bipolar Affective Disorder during the course of ones life is about 1-3%. The bipolar disorders develop, on average, at an earlier age than the unipolar depression. Many people with bipolar disorders developed first symptoms around the age of 15, with the fully developed bipolar disorder between the age of 18 and 35.
Most bipolar disorders do not begin with a depressive episode but with a manic or hypomanic episode. On the other hand about 20% of all people who suffer from depression, develop in the course of the disease hypomanic or manic symptoms.
In contrast to the unipolar depressive disorders, the are no gender differences in the frequency of occurrence of bipolar disorders. Nevertheless, a special form of bipolar disorder, the “rapid cycling”, i.e. the occurrence of at least four episodes of illness in one year, affects in approximately 80-90% women.